Gas-turbine blade



Apr l 1931. H. HQLZWARTH 1,391,427

GAS TURBINE BLADE Original Filed March 12. 1927 mu M Patented Apr. 21,1931 UNITED STATES PATENT OFFICE HANS HOLZWAR-TI-I, F DUSSELDGR-F,GERMANY, ASSIGNGR T0 HOLZVJARTH GAS TUR- BINE 00., OF SAN FRANCISCO,CALIFORNIA, A CORPORATION OF DELAWARE GAS-TURBINE BLADE Applicationfiled March 12, 1927, Serial No. 174,891. Renewed August 30, 1930.

The efiiciency with which heat is utilized in turbines driven by hotmotive agents, and particularly by hot combustion gases, depends largelyupon carrying out the operation at temperatures as high as possible.This requires not only that the turbine blades and the reversing bladesbe made of a material very resistant to heat, but also that properprovision be made for dissipating the heat ab sorbed by the blades. Theheat absorbed by the rotor blades is to be carried away to the rotorbody and the heat absorbed by the reversing blades is to be conductedaway to the casing in which the annular set of reversing blades ismounted. A calculation based on theory and checked with the aid ofpractical experience will determine the length, measured in thedirection in which the gases flow, to be given to the blades of therotor and of the set of reversing blades. This length will alsodetermine the blade crosssection available for carrying away the heat,if, as is customary, the blade is made rectangular in a cross-sectiontaken in a plane 1 passing through the axis of rotation, that is to say,if the foot or base of the foot or attached portion of the blade is madeof a size corresponding to the projection of the blade into said plane.

According to the present invention, superior results are obtained bymaking the blades of a cross-section which, instead of beingrectangular, increases in width toward the foot or attached portion, andin the preferred form of the invention the cross-section of the blade inan axial plane and likewise that of the foot is trapezoidal.

Through this form of the blade, the ad vantage is obtained first of allthat its reduced 40 top portion takes up less heat than it would if theblade had throughout a rectangular cross-section of the width of thefoot, which rectangular form would lead to overheating of the blades.Furthermore, by means of the widened foot the heat taken up from the toppart is conducted better into the rim of the wheel than if the foot wereonly as wide as the top portion. If the foot of the blade, which issecured in the rim of the wheel, were of rectangular cross-section, thenhere again sipation of heat at the outside of the wheel is favored, sothat at this point also local over-heating is prevented.

Without restricting myself to the specific details shown, I will nowproceed to describe typical and satisfactory embodiment of my inventionas illustrated by the accompanying drawings, in which Fig. 1 is afragmentary axial section of a turbine provided with my improvements;Fig. 2 is a detail view in elevation of one of the rotor blades adjacentto the gas nozzle, looking from the right in Fig. 1, and Fig. 3 is across-section of such blade taken on the line 33 of Fig. 2.

At 9 I have indicated a portion of the stationary frame or casing of theturbine, which casing contains a water-cooled nozzle 10 through whichhot combustion gases from a suitable source are discharged against anannular set of blades 2 secured to the rotor body 1 so as to move inunison therewith. The section in Fig. 1 is taken through the axis ofrotation which therefore would be represented by a horizontal line atthe bottom if Fig. 1 were extended downward sufliciently. The drawingshows a second set of rotor blades 2 likewise held to rotate with therotor 1. The blades 2, 2 have feet 4, a respectively fitted intocorrespondingly shaped recesses of the rotor and secured therein bywedges 11. The blades 2 rotate in a path different from the blades 2 andinto the space between them project the stationary reversing blades 3,the general shape and purpose of which are well-known in the art, saidreversing blades being secured rigidly to a ring 8 projecting laterallyfrom the frame or casing 9 and firmly secured thereto. The reversingblades have toothed feet 5 for fastening them on the ring with the aidof wedges 12;

According to the form of my invention illustrated, the rotor blades, 2,2 and the reversing blades 3 are made trapezoidal in axial section, thatis to say, their free ends are narrower than their attached portions,the blades 5 tapering toward said free ends. Thus an efficient path ofgradually increasing width is provided for the passage of heat from theblades 2, 2, 3 through their feet 4, l and 5 respectively to the rotorbody 1 and to the ring 8 respectively, and the transfer of heat thustakes place more efliciently than when the bladesare of uniformcross-section or rectangular shape in axial section, as has beencustomary hitherto. \Vith the rectangular blades of earlierconstruction, the heat is not carried off so readily and the bladestherefore retain a temperature which endangers their strength. Owing tothe better cooling effect obtained with my invention, the blades 2, 2, 3are enabled to resist the heat effects much more reliably than whenemploying the rectangular shape above referred to.

In order to prevent a local accumulation of heat in the rotor body 1, Ihave found it desirable to make the toothed feet 4;, l likewise oftrapezoidal or tapering cross-scction, as shown in Fig. 1, the feet 4,l, however, tapering in a direction opposite to the blades 2, 2', sothat the maximum cross-section will be at the point where the bladesemerge from y the rotor body 1. I thus avoid the danger of heataccumulation, particularly in that portion of the rotor l which liesbetween the feet 4 and the feet at. This shape of the feet also 85promotes the dissipation of heat toward the outside of the rotor bodyand assists in keeping it reasonably cool. For a similar purpose Iprefer to taper the feet 5 in a direction opposite to the tapering ofthe reversing 40 blades 3, so that the maximum width will I again be atthe point where the reversing blade emerges from the ring or member 8 inwhich it is mounted, or, in other words, at the joint of the bladeproper with the foot of the blade. It will be seen that the rotor body 1constitutes a carrier for the blades 2, a and 2'. 4, and similarly thering 8 constitutes a carrier for the reversing blades, 3, 5.

Various changes in the specific form shown and described may be madewithin the scope of the claim without departing from the spirit of myinvention.

I claim: A turbine adapted for operation by a hot driving medium,provided with a blade having an active portion adapted to be impingedupon by said driving medium and with a foot portion, both said footportion and said active portion increasing in width from their anopposite ends toward their adjacent ends,

and a carrier in which said foot portion is 5 mounted.

HANS HOLZVVARTH.

